1. Field of the Invention
This invention relates to pneumatic plug devices for sealing pipelines or conduits. Particularly, this invention relates to pneumatic test plugs for sealing or restricting flow at access ports and tee-connections of low pressure pipelines or conduits.
2. Description of the Related Art
Low pressure pipelines and conduits are common plumbing elements of virtually all residential and many commercial structures. These types of pipes often contain access ports and tee-connections which are normally utilized for cleaning and inspecting purposes. The tee-connections are normally circular in shape and are often internally threaded to receive a threaded closure cap.
The pneumatic pipe plug device of this invention permits a user to utilize an access port or tee-connection and to seal the pipeline or restrict the flow of fluid passing through. Such a utilization allows the user to test the pipe for leakage, vary flow rates, or for similar purposes.
Numerous plugs for sealing tee-connections have been previously proposed. Most of these devices have typically been complex structures which have been difficult or expensive to manufacture. For example, U.S. Pat. No. 4,658,861 to Roberson (hereinafter "the '861 patent") discloses a test plug assembly for pressure testing fluid drains and vent systems. Utilizing an inflatable body and a rigid holder portion which are united by a valve stem, the '861 patent construction is difficult and expensive to manufacture. Furthermore, uniting the inflatable body and the rigid holder portion require a relatively harder elastomeric material which may compromise proper sealing of the plug assembly in some conduit structures.
In an effort to overcome the difficulties associated with the '861 invention U.S. Pat. No. 5,353,841 to Mathison et al. (hereinafter "the '841 patent") disclosed a pneumatic plug for clean-out tees which uses a retention collar to secure the elastomeric body to the rigid end cap. While the '841 invention did address some of the shortcomings of the '861 patent, the '841 patent still required a complex construction and procedure in order to join the retention collar to the end cap.
The pneumatic pipe plug according to the teachings of this invention overcome the difficulties, limitations and other shortcomings of these prior art devices.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. .sctn. 1.56(a) exists.